Microorganisms continue to cause acute and chronic problems for mammalian hosts. These are microorganisms which when administered in sufficient quantities may benefit health through their influence on the host and its microflora. Although utilized for years to manage a variety of conditions, often with encouraging results, there are still questions concerning the effectiveness of probiotic microbes for improving human or animal health. Some of these questions may be due to an inadequate understanding of the mechanisms involved in the actions of these microbes and the means to effectively produce, administer, and evaluate these agents. The American Academy of Microbiology plans to convene a colloquium on "Probiotic Microbes: The Scientific Basis " November 4-6, 2005 in Philadelphia, Pennsylvania. The central goal of this culloquium is to critically examine a series of questions concerning probiotic microbes and their use so that their promise can be more fully achieved. These discussions should help point the way toward further research and actions to establish the utility of probiotic microbes as an important tool in veterinary and clinical medicine. Specific topics to be considered are: 1. Consequences of Normal Flora Acquistion; 2. Advantages of Microflora Manipulation; 3. Mechanisms for Beneficial Host-Microbe Interactions; 4. Mechanisms for Beneficial Microbe-Microbe Interactions; 5. Availability of Systems to Assess Candidate Probiotic Microbes; 6. Regulatory Issues Impacting Probiotic Development. An international group of experts on the various facets of the science concerning probiotic microbes will gather to consider each of these topics in a setting and format that encourages open and vigorous discussions. The deliberations will form the foundation for a report, that will include a succinct description of the issues, graphical representations,and recommendations for future actions. The relevance of this research to public health is to address a better understanding of the microbiology of probiotic microbes, their mechanisms of action, options for optimizing and evaluating their effectiveness, and regulatory concerns focusing in product quality, safety, and efficacy. [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]